Format specification for diagnostic tests

Each diagnostic test consists of a single .kt file containing the code of one or several Kotlin or Java source files. Each diagnostic, be it a warning or an error, is marked in the following way:

<!DIAGNOSTIC_FACTORY_NAME!>element<!>

where DIAGNOSTIC_FACTORY_NAME is the name of the diagnostic which is either:

• a constant from one of the Errors*/Fir*Errors classes;
• a debug diagnostic implemented specifically for the test infrastructure (e.g. DEBUG_INFO_EXPRESSION_TYPE).

To test not only the presence of the diagnostic but also the arguments which will be rendered to the user, provide in parentheses after the diagnostic name a string representation of all of them delimited with ;:

return <!TYPE_MISMATCH("String; Nothing")!>"OK"<!>

If you're unsure what text should be added for the parameters, just leave the string representation empty:

return <!TYPE_MISMATCH("")!>"OK"<!>

and the failed test will present the actual values in the assertion message.

Directives

Read more about test directives here.

Below is the list of some (but not all) directives supported by the test infrastructure.

FILE & MODULE

Read more about the FILE and MODULE directives here.

LANGUAGE

This directive allows you to enable or disable certain language features. Language features are named as entries of the enum class LanguageFeature. Each language feature can be enabled with +, disabled with -, or enabled with a warning with warn:.

Usage:

// LANGUAGE: -TopLevelSealedInheritance

// LANGUAGE: +TypeAliases -LocalDelegatedProperties

// LANGUAGE: warn:Coroutines

DIAGNOSTICS

This directive allows you to exclude some irrelevant diagnostics (e.g. UNUSED_PARAMETER) from a certain test or to include others.

The syntax is:

'([ + - ] DIAGNOSTIC_FACTORY_NAME | ERROR | WARNING | INFO ) +'

where:

• + means ‘include’;
• - means ‘exclude’.

Diagnostics are included or excluded in the order of appearance (e.g. +FOO -BAR means “include FOO but not BAR”).

Usage:

// DIAGNOSTICS: -WARNING +CAST_NEVER_SUCCEEDS

// DIAGNOSTICS: -UNUSED_EXPRESSION -UNUSED_PARAMETER -UNUSED_VARIABLE

CHECK_TYPE

This directive adds the following declarations to the file:

fun <T> checkSubtype(t: T) = t

class CheckTypeInv<T>
fun <E> CheckTypeInv<E>._() {}

infix fun <T> T.checkType(f: CheckTypeInv<T>.() -> Unit) {}

These declarations allow you to check an exact type of an expression in the following way:

fun test(expr: A) {
   expr checkType { _<A>() }
}

In diagnostic tests, CHECK_TYPE directive also disables diagnostics related to usages of _ as a name.

Usage:

// CHECK_TYPE

CHECK_TYPE_WITH_EXACT

This directive adds the following declarations to the file:

@Suppress("INVISIBLE_MEMBER", "INVISIBLE_REFERENCE")
fun <T> checkExactType(expr: @kotlin.internal.Exact T) {}

@Suppress("INVISIBLE_MEMBER", "INVISIBLE_REFERENCE")
fun <T> checkTypeEquality(reference: @kotlin.internal.Exact T, expr: @kotlin.internal.Exact T) {}

Like the CHECK_TYPE directive, these declarations allow you to check an exact type of an expression:

fun test(expr: A) {
    checkExactType<A>(expr)
    checkTypeEquality(A(), expr)
}

Unlike the CHECK_TYPE directive, these declarations:

• can be used in e.g. codegen tests (as codegen tests don't disable diagnostics related to usages of _ as a name);
• don't require you to explicitly specify the type if you have a reference expression of this type (which is useful when checking for non-denotable types).

Usage:

// CHECK_TYPE_WITH_EXACT

API_VERSION

This directive emulates the behavior of the -api-version command-line option, disallowing to use declarations annotated with @SinceKotlin(X) where X is greater than the specified API version. Note that if this directive is present, the NEWER_VERSION_IN_SINCE_KOTLIN diagnostic is automatically disabled, unless the corresponding DIAGNOSTICS directive is present.

Usage:

// API_VERSION: 1.0

RENDER_DIAGNOSTICS_MESSAGES

This K2-specific directive forces the test infrastructure to print diagnostic arguments for all diagnostics.

Usage:

// RENDER_DIAGNOSTICS_MESSAGES